The use of cold or heat therapy has long been known in the medical field. Cold therapy may be used to treat certain limb injuries, such as sprained or strained arm or leg muscles, or injuries to joints. Generally, cold may be applied to these types of injuries to slow blood flow, which reduces swelling, pain, and further damage. Heat therapy may be used to warm or limber muscles by increasing blood flow. For example, athletes may apply heat to thighs or calf muscles prior to an athletic event. In another application, a small chemical heat pack commonly referred to as a “heel warmer” is activated and placed against the foot of a newborn infant to increase the infant's blood flow prior to drawing a blood sample.
A number of products may be used to provide heat or cold therapy. For example, chemical heat or cold products involve a bag or pack containing two or more reagents separated by a membrane. When the user ruptures the membrane, the reagents mix and undergo either an exothermic or endothermic reaction. This type of product provides the user instant heat or cold. When the heating or cooling effect subsides, the product is disposed of. Other thermal therapy products, for example, gel-based hot or cold packs, are reusable but require the user to supply external energy before use, e.g., heat from a microwave oven or cold from a freezer. These products are often less effective than instant chemical hot or cold packs because they are unable to maintain the desired minimum or maximum temperature.
The thermal therapy techniques of the prior art present two challenges. First, many disposable thermal therapy products, while convenient, are unable to deliver or absorb heat for an extended duration. Second, many existing thermal therapy products cause temperature spikes that may result in discomfort to the user, while others are unable to attain the desired therapeutic temperature. Thus, there is a need for a device that provides an extended therapeutic benefit at the desired temperature while eliminating undesirable temperature peaks.